Control of Adiabatic Liquid/Vapor Flow Utilizing EHD Conduction Pumping Mechanism

2004 ◽  
Author(s):  
Yinshan Feng ◽  
Jamal Seyed-Yagoobi
Keyword(s):  
Mass Flux ◽  
Two Phase Flow ◽  
Finite Thickness ◽  
Flow Distribution ◽  
Vapor Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Phase Liquid ◽  
Liquid Vapor

Unlike the electrohydrodynamic (EHD) induction and iondrag pumping, the conduction pumping is associated with the heterocharge layers of finite thickness in the vicinity of the electrodes which are based on the process of dissociation of the neutral electrolytic species and recombination of the generated ions. The conduction term here represents a mechanism for electric current flow in which charged carriers are produced not by injection from electrodes, but by dissociation of molecules within the fluid. This paper presents the control of adiabatic two-phase (liquid/vapor) flow distribution with EHD conduction pumping mechanism at two mass flux levels, Gtotal = 50 kg/m2s and Gtotal = 100 kg/m2s. The effects of the vapor quality, ranging from 0 to 26%, on the EHD conduction pumping have also been experimentally investigated. The measured pressure data show that the EHD conduction pumping can significantly decrease the pressure drop of the two-phase flow. It is also found that the performances of the EHD conduction pump are related to the mass flux and quality of two-phase flow.

Flow Distribution Control Between Two Parallel Meso-Scale Evaporators With Electrohydrodynamic Conduction Pumping

2016 ◽  
Author(s):  
Lei Yang ◽  
Michal Talmor ◽  
Jamal Seyed-Yagoobi
Keyword(s):  
Two Phase Flow ◽  
Finite Thickness ◽  
Flow Distribution ◽  
Control Technique ◽  
Working Fluid ◽  
Phase System ◽  
Phase Flow ◽  
Two Phase ◽  
Macro Scale ◽  
Meso Scale

Electrohydrodynamic (EHD) conduction pumps generate pressure to drive dielectric liquids via the electrical Coulomb force exerted within heterocharge layers of finite thickness in the vicinity of the electrodes. By applying an external electric field in a dielectric liquid, the heterocharge layers form due to the net charges as a result of the process of enhanced dissociation of neutral molecules versus the recombination of the generated ions. EHD conduction pumping can be applied to enhance and control mass and heat transfer of both isothermal and nonisothermal liquid and two-phase fluid, with many advantages such as simple design, no moving parts and low power consumption. It also shows its potential as an active control technique for flow distribution for multi-scale systems in both terrestrial and microgravity environment. Flow distribution control based on EHD conduction pumping mechanism was previously investigated in macro-scale. This study experimentally examines its capability in controlling two-phase flow distribution between two parallel meso-scale evaporators. The working fluid was refrigerant HCFC-123. It has been found that an EHD conduction pump could effectively control the two-phase flow distribution via adjusting the flow rate in each branch line, and facilitate the recovery from dry-out condition in two-phase system.

Complete Condensation of Forced Convection Two-Phase Flow in a Miniature Tube

1999 ◽  
Vol 121 (4) ◽  
pp. 904-915 ◽  
Author(s):  
E. Begg ◽  
D. Khrustalev ◽  
A. Faghri
Keyword(s):  
Two Phase Flow ◽  
Film Condensation ◽  
Vapor Flow ◽  
Pressure Jump ◽  
Phase Flow ◽  
Two Phase ◽  
Vapor Interface ◽  
Complete Condensation ◽  
Annular Film ◽  
Liquid Vapor

A physical and mathematical model of annular film condensation in a miniature tube has been developed. In the model the liquid flow has been coupled with the vapor flow along the liquid-vapor interface through the interfacial temperature, heat flux, shear stress, and pressure jump conditions due to surface tension effects. The model predicts the shape of the liquid-vapor interface along the condenser and the length of the two-phase flow region. The numerical results show that complete condensation of the incoming vapor is possible at comparatively low heat loads. Observations from a flow visualization experiment of water vapor condensing in a horizontal glass tube confirm the existence and qualitative features of annular film condensation leading to the complete condensation phenomenon in small diameter (d < 3.5 mm) circular tubes.

Influence of Vertical Return Bend on the Two-Phase Flow Pattern in 3-mm Minichannel

2003 ◽  
Author(s):  
Ing Youn Chen ◽  
Chi-Chung Wang ◽  
Pi-Shan Huang ◽  
Bing-Chwen Yang ◽  
Yu-Juei Chang
Keyword(s):  
Flow Pattern ◽  
Mass Flux ◽  
Annular Flow ◽  
Two Phase Flow ◽  
Visual Observation ◽  
Phase Flow ◽  
Vapor Quality ◽  
Two Phase ◽  
Total Mass Flux

This study provides a qualitatively visual observation of the two-phase flow patterns for air-water mixtures inside a 3 mm smooth tube with the presence of vertical return bend. The curvature ratio (2R/D) is 3.2 whereas the total mass flux is from 70 to 800 kg/m2 s. The flow can be either entering from the upper of the tube or from the lower tube. However, it is found that there is no great difference between those flow entering at the upper tube and that of the lower tube if the inlet mass flux and vapor quality is the same. For a mass flux of 70 kg/m2 s at a vapor quality to 0.009, as the flow is approaching the return bend, one can observe a fluctuating phenomenon at the tail of the long slug that leads to a liquid ripple around the periphery. When the air slug is trying to penetrate the preceding liquid in the return bend, the shape at the front of the air slug was sharpened. A further increase of the vapor quality to 0.05, the flow after the return bend was temporarily turned from stratified flow into the annular flow. At a higher mass flux of 300 kg/m2 s, unlike those flow pattern at 70 kg/m2 s, the increase of the vapor shear interacts with the centrifugal force and the accumulated liquid within the return bend forces the Taylor bubble to be completely disordered. There is no separating and re-merging phenomenon of the air slug for the slug flow pattern across the return bend even for a very low vapor quality of 0.001. This is quite different from those with larger diameter tube (Chen et al. 2002, Wang et al. 2003b, 2003c).

scholarly journals Variational formulation of stationary two-phase flow distribution

2021 ◽  
pp. 101082
Author(s):  
Niccolo Giannetti ◽  
Mark A.B. Redo ◽  
Kiyoshi Saito ◽  
Hiroaki Yoshimura
Keyword(s):  
Variational Formulation ◽  
Two Phase Flow ◽  
Flow Distribution ◽  
Phase Flow ◽  
Two Phase

Two-phase flow distribution in 2D trickle-bed reactors

1999 ◽  
Vol 54 (13-14) ◽  
pp. 2409-2419 ◽  
Author(s):  
Y. Jiang ◽  
M.R. Khadilkar ◽  
M.H. Al-Dahhan ◽  
M.P. Dudukovic
Keyword(s):  
Two Phase Flow ◽  
Flow Distribution ◽  
Phase Flow ◽  
Two Phase ◽  
Trickle Bed Reactors ◽  
Trickle Bed

Two-phase flow regimes of condensing R-134a at low mass flux in rectangular microchannels

2017 ◽  
Vol 84 ◽  
pp. 92-103 ◽  
Author(s):  
Michael A. Vanderputten ◽  
Tabeel A. Jacob ◽  
Maria Sattar ◽  
Nouman Ali ◽  
Brian M. Fronk
Keyword(s):  
Mass Flux ◽  
Two Phase Flow ◽  
Flow Regimes ◽  
Phase Flow ◽  
Two Phase ◽  
Rectangular Microchannels ◽  
Low Mass ◽  
R 134A

Transient Response of BWR Core Flow During Simulated Generator Load Rejection Event

2009 ◽  
Author(s):  
Masahiro Furuya ◽  
Takashi Hara ◽  
Shinya Mizokami
Keyword(s):  
Mass Flux ◽  
Two Phase Flow ◽  
Differential Pressure ◽  
Phase Flow ◽  
Two Phase ◽  
Core Flow ◽  
Initial Stage ◽  
Rapid Flow ◽  
Fine Control ◽  
Automatic Controllers

Integral Effects Test (IET) was conducted to investigate the effects of flow redistribution during the generator load rejection event by using the SIRIUS-F facility, which simulates boiling two-phase flow in a BWR core. Owing to the automatic controllers of a recirculation pump inverter and fine-control valves in the facility, the time series of signals of heat flux and mass flux were observed to agree well with those of target rapid flow-decrease events in the previous experimental series. This paper addresses the simulated generator load rejection event, during which the flow and power gradually decrease and the flow takes a turn toward recovery. As a result of the two-parallel channel experiment, mass flux of a hot channel is lower than that of the other during the initial stage. When the void fraction becomes smaller, mass flux of the hot channel is observed to become higher. This phenomenon can be accurately demonstrated with the TRAC-BF1 code as well. The code does, therefore, predict the boiling two-phase flow in a BWR core even at such flow-decrease event. During the event, differential pressure along each channel between the upper and lower plena decreases by several tens of kPa. The relative perturbations of the differential pressure between both channels, however, remain less than 0.4%, which is a significantly small amount. In conclusion, the differential pressures between the upper and lower plena of two-parallel channels are, therefore, identical to each other regardless of the power.

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